Hexavalent Chromium EPA Guidance Memo

Guidance for Public Water Systems on Enhanced Monitoring for Chromium-6
(Hexavalent Chromium) in Drinking Water

January 11, 2011

From:
Peter Silva, Assistant Administrator, US EPA

To:
State Drinking Water Agencies
PWS Owners and Managers
Drinking Water Program Managers, Region I-X

EPA appreciates and acknowledges your critical role toward supporting the analytical monitoring requirements for water systems and ensuring all Americans have safe drinking water. Chromium is one of over 90 regulated drinking water contaminants that must be routinely monitored and relies on your analytical expertise. National primary drinking water regulations set the maximum contaminant level (MCL) of 0.1 mg/L for total chromium, which includes chromium-6, however, recent studies indicate the potential for greater human health risks from chromium-6 (the toxic form of chromium) than was previously thought. When EPA completes the human health assessment in 2011, the conclusions will be carefully reviewed and all relevant information will be considered to determine if a new standard needs to be set.

Given this emerging public health information, EPA is providing guidance to all public water systems on ways to enhance chromium monitoring through additional sampling and analysis, specifically for chromium-6 using a slightly modified version of EPA Method 218.6. The Agency is strongly encouraging water systems to consider the recommendations provided on our website and determine how their system might enhance drinking water monitoring for chromium-6. EPA believes that enhanced monitoring will enable public water systems to: better inform their consumers about the levels of chromium-6 in their drinking water, evaluate the degree to which other forms of chromium are transformed into chromium-6 in their drinking water and assess the degree to which existing treatment affects the levels of chromium-6.

National primary drinking water regulations set the maximum contaminant level (MCL) of 0.1 mg/L for total chromium, which includes chromium-6, and requires community and non-transient non-community water systems to test for chromium at the entry point to the distribution system. The chromium standard was established in 1991 based on the best available science. EPA regularly re-evaluates drinking water standards: a rigorous and comprehensive review of chromium-6 health effects began following the release of the toxicity studies by the National Toxicology Program in 2008. In September, 2010, EPA released a draft of the scientilic assessment (Toxicological Review of Hexavalent Chromium) for public comment and external peer review. When this human health assessment is finalized in 2011 , EPA will carefully review the conclusions and consider all relevant inlonnation to determine if a new standard needs to be set.

In the interim period, EPA is providing guidance to water systems on how they may monitor for chromium-6 in addition to the monitoring they are required to perform for total chromium. EPA believes that the enhanced monitoring will enable public water systems to: better inform their consumers about the levels of chromium-6 in their drinking water, evaluate the degree to which other forms of chromium are transformed into chromium-6 in their drinking water and assess the degree to which existing treatment a affects the levels of chromium-6 in drinking water. We appreciate your support and look forward to working with you th rough an increased dialogue between EPA, states, public water systems and the public on issues related to chromium-6.